1. Field of the Invention
This invention generally relates to a positioning apparatus used in a factory and a positioning method using the same, and more particularly to a positioning apparatus and a positioning method using the same for directly positioning a load port of a machine and an overhead hoist transport (OHT) system.
2. Description of Related Art
In a factory of high-technology industry like a semiconductor manufacturing fab, most semi-products are moved via an OHT system to reduce the cost and the possibility of damage due to negligence. The OHT system is generally set above all manufacturing machines, capable of picking one or more semi-products up form a machine after the process in that machine is complete and carrying them to another machine for the next process. Taking the OHT system in an ordinary semiconductor manufacturing fab as an example, it can pick up a front opening unified pod (FOUP) carrying multiple wafers from a machine, move the FOUP to above the load port of another machine, and move the FOUP down to the load port.
Hence, to make the manufacturing process smooth, alignment between the OHT system and all machines is a very important issue. When there is a new machine added in the fab, in order to precisely align the load port of the new machine with the OHT system, one should first align the OHT system with a positioning point in the fab and then align the load port of the new machine with the positioning point. However, such an indirect positioning method will increase not only the positioning error but also the positioning difficulty probably due to a long distance between the positioning point and the machine and/or the hindrances between them.